1. Field of the Invention
This invention is related to a packet communication system with QoS control function, especially applicable to Diffserv.
2. Description of Related Art
Increase of Internet users, follows a sharp increase in the traffic (packets) that flows in the Internet. According to the packet communication mode used in the Internet, one line can carry packets from many users. Therefore, the packet communication mode reduces cost per a bandwidth. And strict management such as QoS (quality of service) control of every user, is not carried out in the Internet. This is also a factor of low cost of the Internet.
Telephone networks and company networks were constructed using exclusive lines respectively. But the low cost of the Internet has caused the movement of integrating telephone networks and company networks into the Internet for reduction of communication cost. For the integration, it is preferable to provide QoS guarantees such as low transmission delay, low packet discard rate, and so on, because those were realized in conventional telephone networks and company networks.
To provide the QoS guarantees, a packet is transmitted based on the priority of the packet that is decided by the agreement between a service provider (SP) and the network user, such as a company, with differentiating the applications, such as telephone traffic, or its respective users.
Japanese Unexamined Patent Publication Disclosure 6(1994)-197128 (related art (1)) shows a packet switching system that an output buffer for CBR and an output buffer for VBR are installed in every each output circuit. The output priority of a packet accumulated to the buffer for CBR is higher than that of a packet accumulated to the buffer for VBR.
Generally, an ATM (Asynchronous Transfer Mode) switching system sets a connection in advance according to an connection information table thereof. The connection information table also stores priority information.
But a router does not have a connection information table because a router, which is used in packet communication mode, does not set up a connection in advance. Therefore, to provide QoS guarantees by a router, it is required a flow detecting means that detects priority information of a packet based on information in the packet header. A router does priority transfer of a packet based on the priority information detected by the flow detecting means. In this specification, a condition for packet discrimination generated by information in the packet header, is called a flow condition. A series of traffic that meets the flow condition is called a flow. And processing that decides whether an input packet meets the flow condition, and decides necessary information for QoS control, such as priority information, is called flow detecting.
Japanese patent Laid-open print No. 6-232904 (related art 2) shows a priority control system in a router that decides relay processing priority from priority information and protocol information of a received packet.
On the other hand, Diffserv (differentiated services) is stated in RFC 2475 of IETF (Internet engineering task force) (related art 3). Using FIG. 2, we explain related art 3. Company networks 221, 222, 223, and 224 are mutually connected by the DS domain 225. The DS domain 225 executes the QoS control based on a policy such as TELNET is preferentially processed. As a result, QoS that contracts in advance between the enterprise network users and an administrator of DS domain 225, is provided. The DS domain 225 is composed of boundary node 226 and boundary node 227 that are positioned in the edge of the DS domain 225 and interior node 228 that is positioned in the core of the DS domain 225. Interior node 228 has much flow. And high-speed lines are connected to interior node 228. Therefore, interior node 228 may not be able to perform QoS control with high speed. Diffserv is a solution to that problem. The Interior node has only limited function because the load of the interior node is higher than that of the boundary node.
Suppose that a packet is transmitted from company network 221 to company network 224. When boundary node 226 receives a packet from company network 221, flow detection means (It is called Classifier in RFC 2475) of boundary node 226 performs flow detecting using the source/destination IP address, the source/destination port number, and the protocol in the TCP/IP header as flow condition. And it decides priority of the packet in the DS domain 225 and writes the priority into the DS field of the packet header. Boundary node 227 and interior node 228 with high load, performs flow detecting and QoS control with high speed based on only DS field value.
In this specification, a network that Diffserv is applied is called a Diffserv network. At the time of shifting to a Diffserv network, there is less possibility of replacement of all existing routers simultaneously because it is required to reduce the cost and the risk following the replacement to a minimum. Therefore, to shift to the Diffserv network smoothly, it is expected that the shift consist of two stages, that is xe2x80x9ctransition stagexe2x80x9d and xe2x80x9cpractical use stagexe2x80x9d.
It is called xe2x80x9chot spotxe2x80x9d that the point in the network that packet discard or increase of transmission delay happens. The router positioned hot spot will be replaced with a router with the powerful QOS control selectively. To reduce a hot spot will improve communication quality.
The router in the transition stage is required a function that performs flow detecting using the source/destination IP address, the source/destination port number, and the protocol in the TCP/IP header as flow condition, and decides the priority of the packet. In this specification, we call this function xe2x80x9cDiffserv Mode 1xe2x80x9d.
In the transition stage, when the replacement to a router with QoS control advances, QoS of the network will improve. When most of routers are replaced to a router with QoS control, the network administrator of the DS domain will start application of the Diffserv network. A router used as an interior node in this stage will be required a function that judges priority information by the DS field. In this specification we call this function xe2x80x9cDiffserv Mode 2xe2x80x9d.
On the other hand, a router used as a boundary node in this stage will be required followings. A router at the exit of the DS domain will be required Diffserv FUNCTION 2. And a router at the entrance of the DS domain 225 will be required a function that executes flow detecting using the source/destination IP address, the source/destination port number, and the protocol in the TCP/IP header as flow condition, and judges the priority of the packet and renewing the DS field in accordance with the result of flow detecting. The function is called xe2x80x9cDiffserv Mode 3xe2x80x9d in this specification.
Therefore, to shift Diffserv network smooth, a router used as an interior node will be required to support xe2x80x9cDiffserv Mode 1xe2x80x9d and xe2x80x9cDiffserv Mode 2xe2x80x9d, and switch the functions in accordance with the stage.
A router used as a boundary node will be required to support xe2x80x9cDiffserv Mode 1xe2x80x9d, xe2x80x9cDiffserv Mode 2xe2x80x9d and xe2x80x9cDiffserv Mode 3xe2x80x9d, and do switching with the functions in accordance with the stage. In practical use stage, a router used as a boundary node will be required to support xe2x80x9cDiffserv Mode 2xe2x80x9d and xe2x80x9cDiffserv Mode 3xe2x80x9d, and do switching the functions. Furthermore, in practical use stage, the Diffserv function switching will be executed in accordance with position in the DS domain 225 such as the edge node or the core node. For example, boundary node A226 will have to apply Diffserv Mode 3 to an input packet from company network 221 and Diffserv Mode 2 to an input packet from interior node 228. On the other hand, interior node 228 will have to apply Diffserv Mode 3 to all input packets. Moreover, an interior node executes xe2x80x9cDiffserv Mode 2xe2x80x9d at high speed because high-speed lines are connected to an interior node.
However, related art 3 does not teach such viewpoints at all.
The object of present invention is to present a router that can do switching with Diffserv Mode 1 and Diffserv Mode 2.
Another object of present invention is to present a router that that can do switching with Diffserv Mode 1, Diffserv Mode 2 and Diffserv Mode 3.
Another object aim of present invention is to present a router that can do switching with Diffserv Mode 2 and Diffserv Mode 3.
Another object of present invention is to present a router that can do Diffserv mode switching in accordance with the position in the DS domain 225 and/or DS domain 225 architecture.
Another object of present invention is to present a router that can execute xe2x80x9cDiffserv Mode 2xe2x80x9d at high-speed.
To achieve the object, a packet communication system of the present invention has at least two modes to apply an input packet of first mode, second mode and third mode, the first mode being a mode that decides priority of the packet by at least one of the address information and the application information, the second mode being a mode that decides priority of the packet by the DS value, the third mode being a mode that decides rewrite the DS value by at least one of the address information and the application information. A control unit of the packet communication system switches a mode to apply an input packet of the modes based on the packet header information of the input packet.